DE1251018B - Process for the production of polyurethane foams - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. CL:

C08g

German class: 39 b-22/04

Number: 1251 018

File number: G 42287IV c / 39 b

Filing date: April 27, 1961

Opening day: September 28, 1967

The invention relates to a method of manufacture of polyether urethane foams with rigid, semi-rigid or flexible cellular structure, which under the Do not suffer any damage under the influence of dry heat.

It is known that hitherto various and varied organometallic compounds have been used as catalysts were used for polyurethane foam production. The most commonly used organometallic Prior art catalysts are organotin compounds such as dibutyltin dilaurate or dibutyl tin diacetate. It has been found that foams made using these catalysts are subject to degradation by the action of heat, so that consumers These substances have to use different agents against the degradation and the stabilizers to get them through to overcome the damage caused by the tin catalyst. Exercise the same adverse influence the organomercury compounds already used as catalysts, e.g. the one in Journ. of Applied Polymer Science, Vol. IV, (1960), Issue 11, p. 208, called diphenylmercury from. As already executed, it is not only the organometallic catalysts still unchanged in the foam product, but also their breakdown products.

They also act as accelerators of the polymerization reaction between reaction products of polyurethanes and amino alcohols on the one hand with polyisocyanates / on the other hand used soluble Heavy metal compounds such as iron acetonylacetonate, titanium tetrabutylate, titanium chloride, copper, cobalt or Manganese acetonylacetonate behave just like the organotin and mercury compounds already mentioned.

The German Auslegeschrift 1 078 321 describes a process for the production of polyurethane foams written from polyethers; in this process, however, polyurethanes with free NCO groups are used first reacted with amino alcohols and then with further diisocyanate, among other things Processed foams. During the formation of the free prepolymer containing NCO groups Heavy metal catalysts, including mercury (II) acetate, used; this conversion results in only more or less viscous, oily products. As far as foams are produced from their reaction products with amino alcohols and polyisocyanates the foaming takes place only in the presence of water with tertiary amines.

It has been observed that in the manufacture of polyether urethanes in bulk the centers of the materials during curing and after the heat process of manufacture
of polyurethane foams

Applicant:

The General Tire & Rubber Company,
Akron, Ohio (V. St. A.)

Representative:

Dr.-Ing. W. Abitz and Dr. D. Morf,

Patent Attorneys, Munich 27, Pienzenauer Str. 28

Named as inventor:

Emery Vincent Braidisch, Tallmadge, Ohio;

George Thomas Gmitter, Akron, Ohio (V. St. A.)

Claimed priority:

V. St. v. America April 27, 1960 (24,900) - -

aging become crumbly and excessively discolored. This disadvantage is particularly pronounced when the flexible polyether urethane foams have been produced by a one-step process in which all components are mixed together at the same time and then subjected to foaming, in particular when certain catalysts have been used. It is not exactly known thereby causing the decomposition of these foams, although this is attributed to the fact can be that the heat required to cause the reaction, including the exothermic heat of reaction causes a reversal of the reaction, possibly due to the Catalyst, the decomposition products of the catalyst and / or the oxygen. Since the cellular Masses themselves act as insulators, a considerable part of the heat is locked in for a considerable time, thereby facilitating this decomposition or reversal. Even if the foams initially have satisfactory properties, they are noticeably decomposed when they are heated for a long time. The method according to the invention enables the production of a flexible polyether urethane cell or foam product according to the one-step process, its resistance to decomposition by Heat is very great, so that no crumbly and no disadvantageous discoloration occur. Even after prolonged aging under the influence of dry heat, little or no occur Decompositions on. The normal lifespan of such a product is thereby extended.

709 649/474

The inventive method for the production of polyurethane foams by single or multi-stage Reaction of at least two OH groups containing polyethers with an average molecular weight between about 600 and 6000, the optionally small amounts of ester-like polyhydroxyl compounds contain ,, and polyisocyanates in the presence of compounds of divalent metals with organic acids as catalysts, blowing agents and foam stabilizers is characterized by that the polyaddition and / or foaming in the presence of compounds of beryllium, Magnesium, calcium, strontium, barium, zinc, cadmium, mercury and / or radium with a Carboxylic acid or with an alkylacetylacetic acid or with a derivative of a ß-diketone or with phenol or with a naphthenic acid as catalysts without the addition of tertiary amines and water, but in Presence of anhydrous, liquid, low-boiling haloalkanes or liquefied hydrocarbon gases is carried out as a propellant. When using these catalysts, the addition of Means to prevent degradation or damage from dry heat aging are superfluous. These catalysts are also useful in the process of making polyurethane foams is carried out using a prepolymer, but its effect is in One-step process is particularly pronounced, since it is precisely here that the decomposition of the flexible material produced has so far been observed Polyurethane foam was particularly noticeable.

It is true that it is not exactly known how the catalysts used according to the invention or their residues prevent heat aging of the polyurethane foams during and after curing or delay ^ however, it is assumed that the result of the relatively strongly exothermic Formation of the foams and the insulating effect of the resulting foam at the same time, heat generated, including heat applied to initiate foaming and curing, not escapes quickly enough. At this stage the catalyst or its residue prevents degradation through this warmth. In the presence of organometallic catalysts other than those according to the invention takes place under these heat conditions and without means against the degradation the reversal of the Reaction or decomposition of the foam.

Those in the process according to the invention alone, i.e. without the addition of tertiary amines and water The organometallic compounds used prevent the possible breakdown by existing free radicals. Possibly these catalysts also react with the polyurethane in such a way that broken ones Urethane, ester or ether compounds are reunited. Your effect or that Their possible decomposition products as powerful antioxidants has already been mentioned. Even if aromatic Diisocyanates, which normally give discolored products on heat aging, are used this discoloration is very much reduced by the use of the catalysts according to the invention.

Reaction products of a polyether and a polyisocyanate can optionally be used as prepolymers with the addition of a triol, which have a relatively high molecular weight, are used, because such prepolymers are relatively stable and shipped from the place of manufacture to the processing plant can be. The prepolymer can after the addition of other hydroxyl-containing substances for the purpose Increase in crosslinking properties and chlorinated and fluorinated alkanes as blowing agents and the catalyst can be processed into a preferably rigid, stable foam. The mixture these substances cause spontaneous foaming.

ίο Flexible or elastic foams are against it most advantageously made by the process of the invention by means of the one-step process. In the one-step process, these are made from polyether, polyisocyanate, blowing agent and the catalyst mentioned existing ingredients mixed together, whereupon the foaming starts spontaneously. This reaction runs more violently, since the polymer growth and the foam formation take place at the same time, while at The use of prepolymers already results in partial polymer growth during the formation of the prepolymer is achieved.

The polyurethane foams produced by the process of the invention are superior to the foams known heretofore in that they do not crumble after curing or after aging, even when aging is carried out at elevated temperatures. For example, it has been found that the foams produced by previously known processes with the usual amine catalysts and the organotin catalysts of tetravalent tin are generally subject to damage or degradation, especially in the middle of the foam, in which the heat development during the exothermic course of the Foaming or later exposure to higher temperatures was greatest. This damage or degradation is manifested through excessive discoloration and fragility and the appearance of crumbly areas. This disadvantage has a particular effect on the foams used to produce upholstery material. Zones of a crumbly nature naturally influence the elasticity of the foam and even lead to a possible bending and collapse of the cushion. The foams produced according to the invention are capable other hand, temperatures of 110 to 14O ⁰ C for many days without any damage or degradation to endure. Although cushioning products are generally not used at these temperatures, this test is used to quickly determine the stability of the product for long periods of time.

The catalyst used in the present invention was found to be useful in the production of all kinds of Polyurethane fabrics, including rigid and semi-rigid foams. These are also catalysts useful in urethane systems in which a major proportion of a polyether and a minor proportion of a Polyester is used, a polyurethane with a larger proportion of ether bonds in comparison to the ester bonds results.

The catalyst used in the process of the invention is either a salt or a salt-like one Compound or complex of the metals beryllium, magnesium, calcium, strontium, barium, Zinc, cadmium, mercury and / or radium.

Compounds of radium are equally well suited as catalysts, but they are eliminated do not use for purely economic reasons.

The carboxylic acids are acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, Caprylic acid, pelargonic acid, capric acid, undecylic acid, lauric acid, myristic acid, palmitic acid, Stearic acid, oleic acid, erucic acid, linoleic acid, linolenic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, Adipic acid, pimelic acid, suberonic acid, azelaic acid, sebacic acid, malic acid, maleic acid, fumaric acid, Tartaric acid, citric acid, benzoic acid, substituted benzoic acid, phthalic acid or the like Formation of the corresponding compounds suitable. The salts of higher monocarboxylic acids with more than 4 carbon atoms, such as stearic acid or oleic acid, are generally preferred. Zinc laurate can e.g. by reacting zinc dust with lauric acid and subsequent drying for removal have been produced by moisture. Beryllium di-2-ethylhexoate or zinc octate is preferred used.

The naphthenic acids used to produce the corresponding naphthenates, which are not completely need to be pure come from the distillation of crude oil.

In the case of the corresponding metal compounds of derivatives of the / S-diketones, the hydrogen atom can the hydroxyl group in the enol form can be replaced by one of the divalent metals mentioned. It a complex product is created in which the metal is coordinated. Examples of /? - diketones are acetylacetone or acetoacetic ester. For example, basic beryllium carbonate is used with 2,4-pentanedione implemented in a known manner. These salt-like compounds can also be obtained by implementing the corresponding metal carbonate with distilled acetylacetone in a slightly acidic, aqueous solution with subsequent Ammonia treatment. This implementation is in "Inorganic Synthesis", Vol. Π, (1946).

Another suitable type of catalyst, which is essentially a complex compound, is by Implementation of one of the metals mentioned with alkylacetylacetates obtained, e.g. by reacting the acetoacetic ester with the corresponding metal carbide.

One type of catalyst that can be used in accordance with the invention are the corresponding phenate salts. Own this the formula

- O - M - O

wherein M is the divalent metal and R is an alkyl substituent or is hydrogen, where the R radicals can be identical or different.

As already mentioned, the catalyst is used in a relatively small amount compared to the weight of the polyether, but in such an amount as is necessary to catalyze the reaction between the polyisocyanate and the polyether (s) and to prevent degradation by dry heat . Although the amounts can vary within a relatively wide range depending on the molecular weight of the catalyst and / or polyether, large amounts are detrimental and can lead to changes in the desired physical properties in the resulting polyurethane foam. In general, about 0.05 to 3.0 weight percent salt of the catalyst in the process according to the invention, based on the weight of the existing polyether, comparable · turns.

The catalyst is added either to the polyether itself or to the prepolymer. He can too can be added to the polyisocyanate provided none of the other reactants are present or the other ingredients prior to the polyurethane formation reaction. However, it can also do everything Components are added at the same time.

ίο 'This is particularly the case with the one-step procedure all polyurethane-forming materials are mixed together at the same time, is desirable.

The prepared by the method of the invention; Foams can be solid, porous, pliable, rigid, or semi-rigid. The degree of flexibility, stiffness and / or porosity depends on the degree of linearity or branching of the polyether or polyisocyanate away. To form the foams, chain-branched polyethers or a larger amounts of these polyethers are used.

The polyethers used (polyalkylene ether glycols) can e.g. from alkylene oxides, glycols, heterocyclic ethers and other compounds by polymerization, copolymerization or the like.

have been received.

With some polyurethane approaches, additional crosslinkers are superfluous. However, if this is used they can contain two to eight or more reactive hydroxyl radicals. Your molecular weight can be low, but it can also be as high as that of the aforementioned polyethers, which are highly branched are, such as reaction products of glycerol and propylene oxide or hexanetriol and propylene oxide or other polyethers. Other substances that can be used as crosslinking polyols are pentaerythritol, Glycol, glycerine, trimethylolpropane, phenyltrimethylolmethane, 1,2,4-butanetriol, 1,1,1-trimethylolhexane, Pentaerythritol monooleate, 1,4-butanediol, 1,2,6-hexanetriol, N, N, N ', N'-tetrakis (2-hydroxypropyl) ethylenediamine, the reaction product of sucrose with 8 equivalents of propylene oxide, which is a compound of 36 carbon atoms and eight reactive hydroxyl groups represents. Mixtures of these compositions are also useful.

The polyethers should contain at least 3 carbon atoms between the ether bonds in order to to avoid being sensitive to water. However, ethylene bonds may be present, provided that a substantial portion of the other bonds contain three or more carbon atoms. Although unsaturated Polyethers and polyols can be used, is preferred saturated or practically saturated Substances to use. The polyethers are also said to be principally or essentially terminated Be provided with hydroxyl groups. In addition, it is preferred that the hydroxyl groups are primary or secondary are. Particularly preferred are the polyethers and crosslinking agents, their hydroxyl groups are primary OH groups, as this improves the stability in the heat.

As stated earlier, smaller amounts of polyester or polyester polyethers can be mixed with the polyethers can be used as long as the polyurethane formed or the polyurethane mixture obtained has a larger one

or has a predominant proportion of ether bonds compared to the ester bonds, so that the Polyurethane is to be regarded as a polyether urethane. The essentially or predominantly linear and

with terminal hydroxyl groups provided polyesters should have an average molecular weight of about 600 to 3000 or even more and an acid number of less than 10, preferably less than 3, own. The polyester is generally aliphatic by esterification of at least one dibasic acid or an anhydride, thereof with at least one glycol prepared. Ratios of More than 1 mole of glycol to acid are used to maintain chains that have a preponderance of terminal ends Have hydroxyl groups. The acids used to make the linear polyesters are generally aliphatic dicarboxylic acids of the formula

HOOC - R - COOH

wherein R is an alkylene radical having 2 to 8 carbon atoms. Preferably these have acids the formula

HOOC (CH ₂ ) ^ COOh

wherein χ = 3 to 8. The anhydrides or mixtures of the acids and their anhydrides can also be used. In the production of linear polyesters, the glycols preferably have the formula

HO (CH ₂ ) ^ OH

where y = 4 to 8. Mixtures of glycols can also have been used. Examples of glycols which can be used are 1,4-butanediol, 1,6-hexamethylene diol or 1,8-octamethylene diol. The polyesters can also have been made by transesterification and other known methods. Mixtures of polyester can also be used.

If branched-chain polyesters are desired, these can be achieved by reacting polyols such as Glycerin, hexanetriol or pentaerythritol have been made with dicarboxylic acids and other polycarboxylic acids be.

The polyesters can also be made with smaller amounts of diamines or amino alcohols to obtain polyesters with a small number of amide bonds and terminal amino groups. However, the diamines or amino alcohols should be used in an amount of 25 mole percent or less so that the polyester has a preponderance of ester bonds and a smaller proportion contains amide bonds and must be regarded as a polyester.

The glycerides of ricinoleic acid, castor oil, alkyd resins or the like can also be used in smaller amounts will.

If the polyethers, polyesters and polyols are not completely pure or contain traces of catalyst and the like, who would have the tendency to accelerate their reaction with polyisocyanates, they can, if rapid reactions are undesirable, washed or otherwise pretreated be to lessen this activity. The polyisocyanates can, for. B. recrystallized to purify them or be distilled.

The organic polyisocyanate used in the practice of the invention can be any polyisocyanate with two, three or more functional or reactive isocyanate groups. You can use aromatic, be aliphatic or aliphatic-aromatic compounds.

Mixtures of the polyisocyanates can also be used, e.g. a mixture of 80:20 or 65:35 of 2,4- or 2,6-tolylene diisocyanates. A preferred class of diisocyanates to be used are the tolylene diisocyanates of the general formula

OCN, R

NCO

where R is hydrogen, methyl, ethyl, propyl, isopropyl, Means butyl, amyl, hexyl or other low molecular weight alkyl radicals.

The amounts of polyether used, optionally crosslinking agent, polyether polyester mixture and Polyisocyanate, depend on the degree of chain length and the desired crosslinking, as well as on the type of polyether or polyisocyanate used and the type of end product desired and its properties. In general, from about 0.5 to 12 equivalents of isocyanate per equivalent of polyether hydroxyl or polyether-polyester (mixed) hydroxyl and about 0.05 to 5 equivalents of polyol crosslinker

hydroxyl per equivalent of polyether hydroxyl or polyether ester (mixed) Hydroxyl can be applied. The product obtained by the process of the invention may contain residues of hydroxyl or isocyanate groups contain, or the reactants can be balanced so that the end product contains practically no unreacted isocyanate and / or hydroxyl groups. In some cases a product with a remainder of isocyanate groups is preferred in order to achieve any desired post-curing facilitate.

As a propellant, for. B. can be used:

the liquid fluorine- or chlorofluoroalkanes, liquefied

Hydrocarbon gases such as methane or ethane. It

■ Mixtures of the liquefied gases can also be used will. The liquid organic blowing or foaming agents can be used in an amount of about 2 to 40 percent by weight, preferably from 9 to 30 percent by weight, based on the total weight of the polyurethane-forming substances.

Other substances can also be added to the reaction mixture, e.g. B. Silicones, such as siloxaneoxyalkylene block copolymers or silicone oils. Also hydrocarbon-substituted silanes, such as vinyltriethoxysilane, Butyltriäthoxysilan, Amyltriäthoxysilan or other monomeric and polymeric organic Silanes, are also useful. In the case of foams of the polyether polyester type, only small amounts should be used Quantities of silicones are used, while with the polyethers far larger quantities are applicable.

The emulsifiers which may be used are preferably either anionic or nonionic or non-acidic or practically non-acidic. Wetting agents, carbon black, TiO ₂ , SiO ₂ -containing substances, wood flour, metal shavings, organic and inorganic, synthetic and natural fibers, e.g. B. wool, cellulose, nylon or glass, surface treated or not, dyes and colored pigments, antioxidants, deodorants, fungicides, plasticizers, rubbers, resins, fire retardants and the like are also useful additives in the reaction mixture.

Antioxidants are not required, since the catalysts used according to the invention are both catalytic as well as the dismantling of own

unite in themselves. If such additional Means to be used to protect against degradation are particularly alkyl-substituted Phenols, Ν, Ν'-dialkyl-substituted phenylenediamines, Alkyl or aryl phosphites. Halogenated organic phosphites, such as halogenated aryl, alkyl, alkaryl, Aralkyl or cycloaliphatic phosphites and mixtures thereof can also be used.

The method according to the invention can, for. B. be carried out in such a way that first the polyisocyanate is reacted with the polyether or polyether-polyester mixture and only then a crosslinking agent is added, but the polyisocyanate can also initially with the crosslinking agent, preferably in Presence of the catalyst, and then reacted with the polyether. The prepolymer from the polyether and the polyisocyanate can be formed in the presence of the catalyst. The addition of a crosslinking agent is superfluous if the one to be used is selected appropriately Polyether only the polyisocyanate reacted with the polyether or polyether-polyester mixture, etc. will. Heat is then added to the reaction mixture in order to control the course of the reaction, e.g. B. to the chain length, cross-linking, cell formation and evaporation or decomposition of the propellant influence or ensure. After curing, the foam can either be heated or aged to improve its properties. Aging can be done in a humid atmosphere will. In addition, in certain cases, the flexible foams are conventionally made according to the Hardening squeezed to the cell walls to increase their permeability to moist steam and to break their elasticity. If heat is applied during squeezing, catalysts can or catalyst products or residues escape if they are vaporizable and not within of the polyurethane itself are included.

The products manufactured by the method according to the invention are available for further processing rubber-like, elastic, flexible, semi-rigid or rigid foams with open or closed Cells particularly suitable, e.g. B. for the production of pillows, fillers, insulating shoes, mattresses, Upholstery for furniture and door panels, insulation for food containers, refrigerators, inaccessible Tube bundles, laminates for panels, building walls, vehicles, buoy elements for boats, buoys, themselves Lifebuoys, life jackets or light reinforcement material for aircraft.

example 1

A rigid foam is made using a prepolymer.

The following raw materials are used to form the prepolymer:

Parts by weight

The propylene oxide adduct of 1,2,6-hexanetriol with a hydroxyl number of 240 .. 100

Hexanetriol-1,2,6 17.93

Tolylene diisocyanate, an 80:20 mixture
of 2,4- and 2,6-tolylene diisocyanate
(TDI) 255

Tri- (2-chloroethyl) phosphite 0.75

Benzoyl chloride (for pH control) 0.06

First the benzoyl chloride and phosphite and finally the propylene oxide adduct and the hexanetriol are added to the TDI located in a reaction vessel. Stirring is then started. The temperature of the mixture begins to rise and reaches about 88 ^° C. Still enough heat is supplied so that the temperature of the reaction is kept between about 88 and 93 ^° C. for about V ₂ to 1 hour or until the reaction mixture is 24.0 Contains% NCO. This is a measure of the extent of the reaction between isocyanate and polyether. The prepolymer obtained with a molecular weight of about 3000 is now combined with the other foaming components according to the following approach:

Components parts by weight

Prepolymer 180

Propylene oxide adduct of sorbitol, C ₆ H ₁₄ O ₆ ,

with a hydroxyl number of about 490 ... 53.0 propylene oxide adduct from polyols with a

Hydroxyl number of 380 74

Trichlorofluoromethane 60

Zinc naphthenate 0.7

These ingredients are poured together into a mold, whereupon they foam spontaneously and fill the mold and overflow. The foam is then ^{cured at 100 °} C. for 15 hours. The foam was found to be uniform in cell size when tested and had a density of 0.024 g / ccm. A section through the foam showed that it is uniform throughout, particularly with regard to the cell size. It does not contain any empty spaces or areas with discoloration or objectionable brittleness.

Further samples of a foam prepared in an identical manner were aged in an oven at 7O ⁰ C. Compressive strength tests showed no loss of strength after 1, 2 and 4 weeks of treatment. The original sample had before aging have a compressive strength of 1.34 kg / cm ² at lO ° / oig ^he compression. At the end of the fourth week the compressive strength was 1.27 kg / cm ² , also with 10% compression.

For comparison, following the procedure of Example 1, with the difference that 0.1 part of dibutyltin dilaurate and 0.4 part of 1,3-tetramethylbutanediamine were used instead of zinc naphthenate, initially a foam of satisfactory foaming strength was obtained, but the cured sample showed on average, zones of discoloration and brittleness, in particular after treatment at temperatures above 70 ^° C. However, decomposition began the longer the foam was exposed to these temperatures. As a result, the foam eventually became crumbly.

Example 2

If according to the method and approaches of Example 1, but with the difference that in the Foam composition instead of zinc naphthenate 1.0 part of a mixture of cadmium and barium stearates was used, a foam was produced, it showed similar properties to that Foam produced according to Example 1. In particular, it withstood dry heat treatment without damage.

'"■" · ■■: ■■ 709649/474

Example 3

The procedure and the approaches of Example 1 were used again with the difference that in the case of foam compound preparation, instead of zinc naphthenate, 1.0 part of strontium naphthenate (8% active strontium) was used. The foam obtained had similar properties to the foam after Example 1. This foam too remained undamaged on treatment with dry heat.

Example 4

If the procedure and the approaches according to Example 1, but with the difference that in 1.0 part of zinc octoate (8% active zinc) was used instead of zinc naphthenate If a foam is produced, it also has properties similar to the foam according to the example 1. It also withstood damage when treated with dry heat. ao

Example 5

Instead of zinc naphthenate, 1.0 part of beryllium di-2-ethylhexoate is used in the foam composition of Example 1, a foam with similar properties to those of the foams is also obtained obtained according to Examples 1 to 4, which suffers no damage when exposed to dry heat will.

Claims (1)

Claim: Process for the production of polyurethane foams by single or multi-stage reaction of at least two OH groups containing polyethers with an average molecular weight between about 600 and 6000, the optionally small amounts of ester-like polyhydroxy compounds contain, and polyisocyanates in the presence of compounds of divalent metals with organic acids as catalysts and blowing agents and foam stabilizers, thereby characterized in that the polyaddition and / or foaming in the presence of compounds of beryllium, magnesium, calcium, strontium, barium, zinc, cadmium, Mercury and / or radium with a carboxylic acid or with an alkylacetyl acetic acid or with a derivative of a /? - diketone or with phenol or with a naphthenic acid as catalysts, without the addition of tertiary amines and water, but in the presence of anhydrous, liquid, Low-boiling haloalkanes or liquefied hydrocarbon gases carried out as propellants will. Considered publications:
German Auslegeschriften No. 1 034 850, 1 078 321. 709 649/474 9.67 © Bundesdruckerei Berlin